1. Field of the Invention
This invention relates to an imaging apparatus used in an electronic imaging system of a digital camera, and in particular, to an electronic imaging apparatus equipped with a photographing optical system in which good performance is obtained even in the use of a CCD with the number of pixels of 3M (mega) or more, the ratio of the entire lens length to an image height can be reduced to 4.5 or less, and a single focus lens with a half angle of view of 25 degrees or more is provided.
2. Description of Related Art
Recently, the compact and high-pixel-density design of an imaging apparatus using an electronic imaging system, such as a digital camera or a mobile phone with a camera, has been increasingly advanced. Consequently, a demand for a compact and high-performance design of a lens system used in such an imaging apparatus has significantly increased.
The single focus lens used in the electronic imaging apparatus, in which its focal length is not changed, is easily used at a half angle of view of 25 degrees or more, in view of the fact that there are various photographic scenes, for example, personal photography, landscape photography, and photography of information such as letters.
Prior art that takes aim at such a half angle of view of 25 degrees or more is set forth, for example, in Japanese Patent Kokai Nos. 2000-321489, 2003-195158, 2001-100092, 2001-21800, and 2000-193884.